Apparatus for preventing freeze-up of refrigerator doors



un 1964 T. D. TAYLOR ETAL APPARATUS FOR PREVENTING FREEZE-UP OFREFRIGERATOR DOORS Filed OCt. 23, 1961 2 Sheets-Sheet 1 was s s 3 m m4 mW w DH w w /.r .8 E M :2 MS a, j M5 u w Z 3. R 0 j 2 4 0 w I I I I I1.11.41. nun LL :HIIIHII. 1 I I .III l 4 2 2 2 J: 2 M T W mmH// June 2,1964 T. D. TAYLOR ETAL 3,135,100

APPARATUS FOR PREVENTING FREEZE-UP OF REFRIGERATOR DOORS Filed Oct. 25,1961 2 Sheets-Sheet 2 l a 5 INVENTORS Donnsfl 72w 0/? ATTORNEYS UnitedStates- Patent O This invention relates generally to apparatus forpreventing freeze-up of refrigerator doors, or the like, and

vmore particularly, is directed to electrical means mounted on the doorof a refrigerator which serves to heat the same, thereby preventing theformation of condensation and frost thereon.

It is a well-known phenomenon that a freezer or refrigerator cabinettends to form condensation and subsequently frost about the door andopening providing access to the cabinet.

The interior of a freezer cabinet is maintained at a low temperature,and, in spite of insulation, the temperature about the door of a cabinetis usually below the temperature of the surrounding air. Moisture in thecooler air surrounding the cabinet opening thus condenses on thesurfaces of the freezer adjacent the opening, and subsequently freezes,causing the door to adhere to the frame thus making it difficult to openand close the door. Although found with respect to all types ofrefrigerator doors, this sticking condition is especially prevalent indoors of the sliding type. It may arise while the freezer door is closedand is aggravated by repeated opening and closing of the freezer door.

In the past, various means have been employed to diminish or eliminatethis condition, including the use of electrically heated strips ofconducting material placed about the periphery of the door frame leadinginto the freezer, and about the door itself. It is well known thatelectrical voltages in excess of approximately volts are painful and cancause harm when received by a human, and therefore, at the line voltagesused in these prior art structures, it was necessary that the heatingelements be completely insulated; otherwise, the devices would be verydangerous in use. The insulation employed in such constructions wasoften expensive and it was usually necessary to build the anti-frostdevice into the refrigerator itself. In an effort to improve thecharacteristics of these prior art devices, the present invention hasbeen made.

.The invention disclosed herein is directed to a frost preventing devicewhich requires no insulation, can be inexpensively manufactured, andwhich can be applied to any presently existing refrigerator door as wellas to a new door.

The invention is illustrated herein in a preferred embodimentwhichcompris'es a strip of uninsulated conducting material formed aboutthe periphery of a freezer door such that it contacts the jamb of thedoor frame when the door is closed. A current transformer mounted on thedoor is provided with electrical leads connected to the primary windingtherein adapted to be plugged into any suitable electrical outlet; Thesecondary winding of the transformer is connected to the electricalconducting material which thereby conducts electrical current at a lowvoltage which is sufficient to heat the strip but which at the same timewill not present any element of danger to a person operating the freezerdoor. The preferred transformer contemplated is to have a primarywinding adapted for connection to a typical 110 volt. A.C. source, and asecondary winding arranged to deliver 30-40 amperes of current at avoltage of 6-8 volts. Such an apparatus will maintain a typicalconducting strip at a temperature of approximately F. when the interiorof the freezer compartment is maintained at a temperature 3,135,100Patented J une 2, 1964 "ice of -5 F., thereby preventing the formationof con densation and frost around the door jamb and outer periphery ofthe freezer door.

Another feature of the invention is the fact that there is no necessityfor a temperature regulating thermostat or switch to be used incombination with the transformer and conductor arrangement justdescribed. The reason for this is that the circuit is of such a designthat the current through the strip is automatically limited. This, ineffect, provides the necessary temperature control.

Accordingly, it is an object of the present invention to provide animproved apparatus for defrosting a refrigerator door and door frame bymeans of a low voltage electrical current passed around the peripherythereof.

Another object of this invention is the provision of a *defrosterapparatus for use in combination with freezers and refrigerators, or thelike, having an insulated door for entrance to or exit therefrom with alow voltage, high current electrical source mounted thereon andconnected to uninsulated conductor means on the door or door framewhereby passage of the electric current through the conductor means willprevent the formation of frost on the door 'without harming oneoperating the door.

A further object of this invention is to provide door frame meanshavinga resilient gasket secured to its periphery and uninsulated conductormeans secured to the door adapted to engage the resilient gasket meanswhen the door is in closed position.

Still another object of this invention is the provision of electricalapparatus to prevent the freeze-up of refrigerator doors which can beeasily and inexpensively applied to existing as well as new refrigeratordoors and door frames.

Other objects and advantages will become more apparent in the course ofthe following detailed description of an illustrative embodiment of theinvention, which may be best understood with reference to theaccompanying drawings in which like parts are designated by likereference numerals throughout the same.

In the drawings:

FIGURE 1 is a front elevation view of a walk-in type refrigerator doorhingedly mounted on the door frame of a freezer and employing theheating apparatus which forms the basis of the present invention;

FIGURE 2 is a side elevation view of the refrigerator door illustratedin'FIGURE l; 7

FIGURE 3 is a rear elevation view of the door illus trated in FIGURES 1and 2, and showing the electrical indicated at '10. A door frame 12 isshown in FIGURE --1 and is suitably mounted in the wall 14 of a freezeror refrigerator. Pivotally mounted by means of hinges 16 to the doorframe 12 is an insulated refrigerator door indicated at 18 which may beopened or closed by means of a latch 20. I

. Although the refrigerator door '18 illustrated in the figures is 'ofthe walk-in type such as is found, for example, in large grocery storeand warehouse freezers, it

is to be understood that the apparatus to be described may be adaptedfor use in home refrigerators or freezers and also in the type offreezer cabinets employing sliding doors for access to the contentsthereof.

A current-type transformer 22 is suitably mounted to the front side ofthe refrigerator door 18. An electrical lead 24 extends from the primarywinding of the trans former 22 and has the other end thereof adapted tobe plugged into the electrical outlet 26 which may be mounted on thedoor frame 12. The electrical outlet may be of a standard typedelivering electrical current at a rated electromotive force of 110volts.

Connected to the ends of the secondary winding of the transformer 22-are a pair of copper bus leads 27' which extend downwardly from thetransformer and around the bottom of the refrigerator door as indicatedat 28, thence upwardly a short distance on the rear side of therefrigerator as is clearly seen in FIGURES-2 and 3. Standard hard drawnbrass Weatherstripping, or other suitable conducting material, asindicated at 30, may 1 be applied to the rear of the door about theperiphery thereof by nailing or by other suitable means. The weatherstripping is preferably overlapped and soldered at the corners in orderto provide a good electrical connection. At the base of'the door thestripping is soldered to the copper bus leads 24'which connect with thesecondary winding of the transformer 22. In operation, the

busses 27 have been satisfactorily made of flat ribbon copper wirehaving a cross section of inch by inch, although it is to be understoodthat the busses may have other cross sectional areas and shapes asdetermined by an expert skilled in the art. Likewise, for a door havingdimensions of approximately 6 /2 feet by 3 feet, brass stripping havingan over-all length of 16 feet and a cross section of 1 /8 inches byinch, has been found to be satisfactory.

Resilient gasket material 32 of rubber or other suitable material issecured to the door frame at 34 which includes the door jambs togetherwith the horizontal members defining the entire doorway about theperiphery thereof as is clearly seen in FIGURE 4. The gasket material 32is mounted upon the door in such a manner that the gasket will be causedto engage the weather stripping 30 mounted on the rear side of therefrigerator door 18 when the door is in closed position.

When the electrical lead 2'4 is plugged into the outlet 26, for example,a 110 vol-t line, the transformer 22 generates current at low voltage inthe secondary winding of the transformer which flows through the copperbusses 27 and the brass stripping 30 connected thereto. The currentthereby provided'will maintain the stripping 30 at a temperature ofapproximately 70 F. when the interior of the refrigerator or freezer isheld at a reduced temperature of approximately --5 F. Of course, it willbe apparent that a transformer having a somewhat different ratio ofprimary to secondary winding turns might be desirably employed if thefreezer temperature is to be substantially greater or less than the -5F. temperature used herein by way of example. i

The defroster apparatus which has been described can be applied to anyexisting freezer door easily and with a minimum of expense since thevoltage is transformed from the 1*10-rating of the line current to. aharmless low voltage, say, 6-8 volts. The stripping 30 may be completelyuninsulated without presenting any element of danger to one entering orleaving the freezer. Furthermore, since the transformer inherentlylimits the current passing through the stripping 30, there is nonecessity in providing the apparatus of' this inventionwith atemperature regulating thermostat or switch.

Although the apparatus of the invention has been described as beingmounted upon a door'leading into a refrigerator or freezer, theinvention is also deemed to encompass amodification as illustrated'inFIGURE 5 wherein it is mounted to the door frame upon which the, door ispivoted. The transformer 22 might conceivably be mounted upon the frame12, the brass stripping 30 being suitably fastened to the jamb means 32about the periphery of the door opening. Employing substantially thesame structure as the apparatus mounted on the door, the frame-mountedembodiment would likewise serve to prevent the formation of condensationand frost in the closure zone of the door 18. At the same time, thevoltages employed are preferably substantially less than 25 volts sothat a person using the door would not be harmed thereby.

While an improved apparatus for eliminating frost or the deposit ofmoisture on the surfaces of a freezer and a door opening thereinto ofthe walk-in type, has been disclosed, it is to be understood, of coursethat the constructions shown are for purposes of description only, andmay be modified in many and various respects, within the scope of theappended claims, without departing from the spirit or sacrificing any ofthe advantages of the invention, and that the invent-ion is not limitedin its application thereto, but may be employed in various other typesof refrigerators and freeze-rs wherever the use of an apparatus of thischaracter is desirable or required.

What is claimed is:

1. Apparatus for preventing the formation of ice and frost about thejunction of doorway members including a door leading into a refrigeratedcompartment and the frame thereof, said apparatus comprising acontinuous electrically uninsulated conductive strip mounted upon theexterior surface of at least one of said doorway members along asubstantial length of the doorway periphery and in close proximity tothe closure zone between the door and frame whereat freezing of waterfrom the air tends to occur as warm air moves past the door into thecompartment, a source of electric current, and means conmeeting the endsof said strip to said source, the voltage ofwthe source being relatedtothe electrical resistance of the closed circuit formed by the'strip andconnecting means so that the maximum voltage across any two pointsof theuninsul-ated portion of said circuit is less than approximately 25vol-ts, and the source having capacity to drive current throughsaidstrip in amount sufficient to heat same sufiiciently to preventfreezing of water in said closure zone.

2. The apparatus set forth in claim 1 wherein said source of electriccurrent comprises step-down transformer means having a primary windingadapted for connection to anelectrical outlet and a secondary windingadapted for connection to said connecting means.

3. The apparatus set forth in claim 1 wherein said uninsulated stripismounted upon said door.

4. The'apparatus set forth in claim 1 wherein said uninsulated strip ismounted upon said frame.

5. The apparatus set forth in' claim 1 wherein said uninsul-atedconductive strip is mounted upon the surface References Cited in the.file of this patent UNITED STATES PATENTS 2,238,511 Thaxter Apr. 15,1941 2,731,804 Grubbs Jan. 24, 1956 2,807,942 Dahlgren Oct. 1, 19572,858,408 Barroero Oct. 28, 1958

1. APPARATUS FOR PREVENTING THE FORMATION OF ICE AND FROST ABOUT THEJUNCTION OF DOORWAY MEMBERS INCLUDING A DOOR LEADING INTO A REFRIGERATEDCOMPARTMENT AND THE FRAME THEREOF, SAID APPARATUS COMPRISING ACONTINUOUS ELECTRICALLY UNISULATED CONDUCTIVE STRIP MOUNTED UPON THEEXTERIOR SURFACE OF AT LEAST ONE OF SAID DOORWAY MEMBERS ALONG ASUBSTANTIAL LENGTH OF THE DOORWAY PERIPHERY AND IN CLOSE PROXIMITY TOTHE CLOSURE ZONE BETWEEN THE DOOR AND FRAME WHEREAT FREEZING OF WATERFROM THE AIR TENDS TO OCCUR AS WARM AIR MOVES PAST THE DOOR INTO THECOMPARTMENT, A SOURCE OF ELECTRIC CURRENT, AND MEANS CONNECTING THE ENDSOF SAID STRIP TO SAID SOURCE, THE VOLTAGE OF THE SOURCE BEING RELATED TOTHE ELECTRICAL RESISTANCE OF THE CLOSED CIRCUIT FORMED BY THE STRIP ANDCONNECTING MEANS SO THAT THE MAXIMUM VOLTAGE ACROSS ANY TWO POINTS OFTHE UNINSULATED PORTION OF SAID CIRCUIT IS LESS THAN APPROXIMATELY 25VOLTS, AND THE SOURCE HAVING CAPACITY TO DRIVE CURRENT THROUGH SAIDSTRIP IN AMOUNT SUFFICIENT TO HEAT SAME SUFFICIENTLY TO PREVENT FREEZINGOF WATER IN SAID CLOSURE ZONE.